Patent Application
20140291981
The present invention relates generally to the reinforced rubber hose industry and in particular to swaged hose couplings used to terminate large diameter high pressure flexible reinforced rubber hose used in the energy, marine, petrochemical and like industries, and which is specifically designed for use in high temperatures in which the rubber softens under temperature and begins to creep.
High-pressure rubber hose is used in many instances in industry, but particularly in the mining, construction, energy, marine and petrochemical industries. Flexible rubber hose is used to transfer fluids under various pressures and temperatures between two points; one or both of which may move relative to each other or to another fixed point in space. Current use of these rubber hoses is beginning to use higher and higher liquid transfer temperatures which affect the reinforced rubber hose dramatically. Essentially, the rubber begins to soften under high temperature and creeps; thereby, making the entire hose system problematic.
Piping at the two points is generally metal (or some other form of fixed conduit), and the flexible hose must attach to the piping at both ends. This requires a coupling on each end of the hose.
In the drilling industry, a flexible rubber hose runs between the pump piping system on the rig and the kelly which is coupled to the rotating drill string. The pump system forces drilling fluid down the center of the drill pipe and back through the wellbore, in order to flush cuttings from the wellbore (plus providing wellbore stability, etc.). In this instance, the flexible hose is subjected to high pressures. The high pressure is required to both transfer drilling fluid into the wellbore and overcome static return head pressures—the deeper the wellbore, the higher the pressure.
The rotary drilling hose is subject to further stress in that it hangs down within the derrick supported at either end by the metal coupling on the hose and the fact that the kelly is moved up and down literally thousands of times during the drilling operation. This means that the hose is subject to stress at the metal coupling (in addition to being subject to stress throughout its length). Thus, a highly reliable bonding between the hose and the coupling is required for protection of personnel and equipment and to hold pressure. If the hose breaks loose from the coupling, it could easily fall and cause severe damage on the drill floor of the rig. In a similar manner, if the hose breaks, circulation may be lost resulting in a well blowout.
In order to obtain a high-pressure flexible rubber hose (the term rubber is used generally and does not specifically mean natural occurring rubber gum) a hose manufacturer incorporates a reinforcing material. Thus, the hose will consist of an inside sealing membrane—the fluid tight element or an inner tube, a reinforcing element, an outer rubber element, and finally some sort of abrasive resistant covering. The inner tube can be rubber, nylon, plastic, corrugated metal or similar type materials. The reinforcing element can be polyester or similar organic material, carbon fiber or similar, high technology material or metal (steel) generally in the form of wire or cable. The reinforcement generally is used in multiple layers called “plys” and is usually made of high tensile steel.
There are different types of reinforcing employed by the hose manufacturer that is set down in even layers—i.e., 2 layers, 4 layers, 6 layers, etc., and grading systems are used to specify burst pressures for hose. For example, in the rotary drilling industry, grade C hose has a minimum burst pressure of 10,000 psi, grade D hose has a minimum burst pressure of 12,500 psi, and grade E hose has a minimum (guaranteed) burst pressure of 18,750 psi. Grade C and D hose are 2 ply hose, although there is some 4 ply D hose. Most grade E hose is 4 ply. Swage end connectors are currently available for two ply hose and therefore the burst pressure range for C and D hoses is covered by the current art except at high temperature where the effect of rubber creep causes the connector to fail. (The objective of this invention.)
Generally a hose manufacturer manufactures flexible hoses to specific order by the purchaser, who specifies length, diameter, pressure, service ratings and required end connections. These flexible hoses are generally referred to as a “hose assembly with end connectors” or “a built-up hose assembly.” This term is used throughout the industry.
In a built up hose assembly with end connections, the manufacturer, during the course of manufacturing, terminates the rubber hose into a metal fitting (the end connector) as specified by the purchaser. Thus, the manufacturer would make the inner rubber membrane (1st Carcass) and its associated inner seal layer (tube) and terminate this assembly in the end connector. The manufacturer would then add the wire reinforcement, as needed, terminating each reinforcing wire (or cable) in the end connector. Two techniques are typically employed by hose manufacturers for terminating the wire reinforcing in or on the end connector itself but are beyond the scope of this discussion. Finally the outer rubber layer (2nd Carcass) and outer cover (cover) would be formed about the reinforcing wire or cable and the overall product vulcanized to achieve a cohesive product. It should be noted that high temperature rubber creep will occur in built-up hoses leading to failure at elevated temperatures.
It takes time to manufacture a hose assembly with built-up end connections, and often such a hose is needed almost immediately by industry. In order to service this demand a separate industry termed the local market distributor has evolved. The local market distributor keeps bulk reinforced hose—hose without connectors—in inventory. The purchaser would specify the hose requirements—diameter, length, pressure rating and end connectors—to the local market distributor. The local market distributor then takes bulk reinforced rubber hose from inventory, cuts the hose to required length, and places a coupling on each end of the hose. Bulk hose is available in varying lengths from a hose manufacturer, and the actual bulk length (between 90 feet [27 m] and 110 feet [34 m]) will depend on the mandrel used by the manufacturer.
The resulting hose is called a SWAGED or CRIMPED HOSE, depending on the method used to “place” the end connector onto the hose, where the term “place” is being used to include both swaging and/or crimping operations. It should be noted that swaging and crimping accomplish similar end results.
The current state of the art in swaged (or crimped) connectors has evolved to using an outer ferrule with nodes (internal ridges) that are compressed around the end of a reinforced hose about a stem that is inserted into the end of the hose. The stem may or may not have barbs that are meant to improve the “grip” between the hose and the end connector. Often, the outer layer of hose rubber is “skived” which means that the outer layer of rubber is removed exposing the reinforcement (although some local distributors do not skive).
The reinforced hose is actually held in the end connector by the ridges of the ferrule gripping the reinforcement via compression of the hose against the stem. The compression operation (swaging or crimping) of the ferrule against the reinforcement and against the inner stem creates severe stress and strain within the inner tube.
Development of high pressure swaged end connectors for rubber hose has extended over a period of years and the art runs the gauntlet from low temperature and/or low pressure to high temperature and/or high pressure applications: except that the high temperatures are becoming higher, particularly in the drilling industry as wells become deeper. Hose diameters vary, and the manufacturers/providers of connectors realize that the pump-off force on the fitting is proportional to the inside diameter of the hose and the applied pressure.
As explained in U.S. Pat. No. 7,388,090 to Baldwin et at., which is incorporated in its entirety in this disclosure by reference, most of the standard prior art uses a serrated stem that has backward facing teeth that grips the inner liner of the hose to retain the stem in the hose. Further the art also uses a series of ridges within the ferrule that bite into the outer layer of the hose and the reinforcement and supposedly causes the teeth (or barbs) of the stem to bite further into the inner lining.
Baldwin et al. explain that the standard art may cause severe failure of the reinforcing cable (or wire) because the sharp edges of the connector damage the reinforcement. In order to overcome this basic failure Baldwin et al. proposed an invention that consisted of a “waved” ferrule and stem that joins an end connector to flexible reinforced rubber hose thereby forming a “double sine-wave lock” between the ferrule and the stem, but mainly the lock forms within the ferrule (see U.S. Pat. No. 7,388,090). The ferrule and stem are welded together at the coupling end leaving an opening, which accepts the reinforced rubber (elastomer) hose in almost the same manner as a normal “ridged” ferrule and “barbed” stem fitting. Rather than having straight sides, the “ridges” of the ferrule and high points of the stem have a sinusoidal shape—a wave. The wave pattern has the appearance of ripples on a pond caused by throwing a stone into the water.
The ‘double sine-wave lock’ invention locks all the plys of hose reinforcement inside the end connector, between the stem, the inner carcass, the reinforcement, and the ferrule, in a sine wave compressed against the ferrule and the stem to give the fitting an overall strength that is in excess of the strength of the free standing hose (without end connectors) whether or not the hose is under pressure. Grade E hose has a minimum burst pressure of 18,750 psi; thus the instant device, when used with grade E hose will have an overall strength greater than 18,750 psi. (At these pressures the pump-off forces involved reach or exceed 240,000 poundsforce depending on the cross sectional areas.) The invention carefully considers the material forming the ferrule and stem and the relative movement of those materials while attaching the end connector to the hose along with the unpredictable qualities of rubber and flexible hose construction to minimize induced stress in the hose reinforcement and the inner tube. All of these factors, including the sinusoidal shape of the ferrule and stem and the preferred two-step method of attachment (internal expansion of the stem followed by external swaging of the ferrule), operate together to form the original Baldwin et al. invention.
In overall summary, the original Baldwin et al. ‘double sine-wave lock’ invention utilizes a sinusoidal wave-like lock within a ferrule and stem to lock the reinforcement plys and the hose into the end connector by compressing the hose (including the inner carcass) and reinforcement between the waved ferrule and waved stem. Stress and strain on the reinforcement and the tendency for the reinforcement to tear (or pull away) from the rubber hose is minimized by carefully reducing the relative axial displacement between the ferrule and stem that always occurs during the attachment operation. The relative axial displacement is minimized by using high tensile strength steels, minimum un-attached clearances between the hose and end connector, and careful design of the node, lands grooves and flutes to cause a sine like wave while minimizing the radial thickness of the stem and ferrule at the critical cross-sections and considering the resulting strength of the attached fitting.
The Baldwin ‘double sine-wave lock’ has proven to work with any cable or wire high pressure reinforced hose and has in fact replaced the ‘built-up’ hose with end connectors, because the hose that utilizes the Baldwin double sine-wave end connector will not fail between the hose and the end connector. Any failure of the hose under pressure will be in the hose itself. The end connector will not come loose from the hose: this statement cannot be made regarding all built-up hoses. Thus, the ‘double sine-wave lock’ Baldwin end connector has improved safety in the workplace. No longer will a hose come loose and flop all over the area damaging equipment and injuring personnel. However, as good as the original Baldwin connector is, it is subject to high temperature rubber creep and therefore its use is limited by fluid temperature.
In a related improvement to the Baldwin sine-wave lock, the inventors wondered if such a two step process was needed, and if large (relatively) lands and grooves were required on the stem. It was known that the actual lock occurred between the ferrule and the reinforcement with some minimal lock (transfer of pump-off force) between the stem and the inner tube onto the reinforcement. If a stem could be designed with small bumps and if a connection step could be eliminated an improved device would result. More importantly, the removal of the expansion step would reduce the amount of material movement within the hose during the expansion/swaging process. With the reduction of material movement within the hose itself, an improved seal and lock could result with a reduction in induced stress. Such a device would work well with the new European light weight high pressure reinforced rubber hose. This hose uses wire reinforcement and uses a much thinner inner tube. The inner tube is the non-leaking flexible conduit through which a high pressure fluid passes. The expansion force is transferred to the reinforcement which prevents the inner tube from bursting. In order to reduce the overall hose weight, manufacturers are using a thin tube and a thin outer cover with multiple spiral-wire reinforcement. As these materials become thinner, the requirement that movement between the components of the hose, (i.e., the inner tube, reinforcement and outer carcass) becomes more critical.
In the most recent series of patent filings (see the above paragraph), Baldwin et al. have discovered that the lands/flutes or node/grooves that are on the stem may be reduced in size and severity. In fact, the severity of the flutes and grooves in the stem has been reduced to a series of matching small bumps, which, when the connector is swaged onto the hose, cause the sine-wave interlock to occur. This technique has been commercially successful and works well at low to medium temperatures for thin wall small diameter hoses. In fact, the key commercial success has been the removal of internal expansion step, which results in less stress on the inner tube and reinforcement. This improvement has been described in the Baldwin et al. U.S. Provisional Application 61/208,531 (filed 25 Feb. 2009), the PCT Application PCT/US2010/000520 (WIPO WO/2010/098833—2 Sep. 2010), U.S. National application Ser. No. 13/138,182, and other national applications throughout the world. It should be noted that this disclosure claims priority from U.S. Provisional 61/514,596 (filed 3 Aug. 2011) which itself is a continuation-in-part of U.S. Provisional 61/208,531.
However, the problem of rubber creep at elevated temperatures continued to cause problems, particularly in applications required to meet some of the new API standards for drilling hose. The inventors found that much to their chagrin, single skived hose (where just the outer cover is removed to expose the reinforcement) will not hold in place as the temperature is raised and the rubber within the hose starts to creep. Furthermore, they discovered that simple internal grippers, without a technique to reduce induced stress on the reinforcement would not solve the issue. Thus, there remains a need for an end connector that will securely grip the reinforcement of a reinforced rubber hose, thereby transferring all the pump-off forces to the metal—both the end connector and the reinforcement, but at the same time retaining any ‘creeping’ rubber or elastomer within the connector/hose assembly thereby assuring a leak-proof, highly reliable, and SAFE assembly.
The invention consists of a series of improvements to the sine-wave lock disclosed in U.S. Pat. No. 7,338,090 to Baldwin et al, wherein the series of improvements are the addition of a series of hose reinforcement grippers within the first section of the end connector (starting at the welded or beveled end of the connector) which form a metal to metal contact with the reinforcement, the addition of an inner tube dam, the addition of the standard Baldwin et al. sine-wave lock in the middle end, and the slightly modified (from U.S. Pat. No. 7,338,090) end section of the connector towards the hose end of the connector. The reinforcement grippers actually grip the hose reinforcement on both sides of the metal reinforcement: this requires “double skiving” or “internal skiving and external skiving” of the reinforced rubber hose. Furthermore the reinforcement grippers are sloped so that the pressure directly exerted on the reinforcement reduces (or tappers-off) going from the open end of the connector towards the hose end of the connector within the hose held by the connector.
The remaining portion of the “standard” Baldwin et al. sine-wave lock concept not only continues to retain the hose within the connector, but also acts to reduce inner tube creep and tearing of the inner tube thus preventing leakage of internal fluids. In addition the incorporation of the improvement in the tapering section of the connector where the end connector meets the outside of the rubber hose continues to reduce creep. The inner tube dam (a key feature) prevents inner tube creep into the reinforcement grippers. The inner tube dam and the improved tapering section act to prevent leakage of internal fluids because both the inner tube and the outer carcass are not allowed to creep. There is both COLD and HOT creep found in the hose: cold creep occurs during and somewhat after the swaging operation, and hot creep occurs when the hose is subjected to high temperature. The stem and ferrule are connected together by a suitable process, such as welding.
The end connector is joined to the reinforced hose in the standard manner which involves skiving the outer jacket plus skiving the inner tube. The two skives are not the same length; however, the outer skive is the same as required for the standard Baldwin et al. device. The inner skive is only as long and the length of the ‘internal grippers.’ The hose is carefully placed within the end connector cavity formed between the ferrule and the stem to the point where the skived hose (inner and outer) rests within the ‘internal gripper’ section and the end of the inner tube rests just past the last flute and within the last land at the termination end of the connector abutting the dam. The fitting is then preferentially double swaged onto the hose by first expanding the stem and then compressing (or swaging) the ferrule. The additional step of first internally expanding and then swaging, reduces the stress on the reinforcement and the inner tube, and further reduces cold rubber creep. (The reader must remember that the reinforcement used in rubber hose is a high tensile strength material, and, as such, it does not react “pleasantly” to pinching. Pinching may cause strain in the reinforcement material which will result in failure under pressure.) The “sloped” interacting grippers exert a varying force on the reinforcement with the greatest force applied at the open end of the hose varying to a minimum force away from the open end.
As the double swaging process occurs, the flutes on the stem create an offset force which causes the reinforcing to expand into the nodes of the ferrule forming the sine-wave lock between the reinforcement and the lands and nodes of the ferrule, and the grippers come into lock with the reinforcement. The double swaging step ensures that, in an alternate embodiment, the internal grippers will first gently pull into the reinforcement during expansion of the stem. Then, as the final swage occurs, the grippers will pull into the reinforcement without damaging the reinforcement applying a minimum lock away from the open end of the hose and a maximum lock at the open end of the hose due to the sloped nature of the grippers in the ferrule. A further internal gripper alternate embodiment may take advantage of the proven sine-wave lock concept employed in the single skived section of the connector and the grippers may be modified accordingly. Similarly, in the section of the hose which is only single skived, the sine-wave lock follows throughout the hose. (It should be noted that the sine-wave lock looks very much like a modified (sine x)/x function: i.e., it is not a perfect sine-wave.)
The stem may be coated, during manufacture or at any time, with a friction reducing material that allows the inner tube of the reinforced hose to more freely slide along the stem during the process that swages (or crimps) the connector to the hose.
In summary, the instant invention utilizes a metal to metal lock between the ferrule, the reinforcement of the hose, and the stem which couples the pump off force to the connector. In addition, the inner tube dam prevents creep of the inner tube elastomer towards the outboard end (open end) of the connector and thus into the reinforcement gripper section. Finally the sinusoidal lock between the ferrule, reinforcement, inner tube and stem coupled with the improved transition to the hose at the hose end (inboard end) of the connector further serve to reduce creep of the inner tube and outer carcass of the hose.
A prototype of the instant invention is shown in
Simple mechanical calculations based on material properties and the degree of swaging that will be applied allow the designer to calculate the land spacing so that after the fitting is swaged to the hose, the flutes of the stem, 15, will fall approximately midway inside the nodes, 10, of the ferrule and vice-versa for the lands, 11, of the ferrule falling approximately midway inside the grooves, 14, of the stem. (See
The dimensions of the nodes and land heights must not be read as a restriction but as a sample. Similarly, the land spacing shown must not be read as a restriction but as a sample. Under some circumstances (larger diameter hose), it may be necessary to adjust these dimensions (and number) so that they vary with distance from the welded end of the connector forming an overall slope. Further the materials of construction must not be as a limitation but as an example.
At the end of the connector nearest the hose, the inside diameter of the ferrule is increased so that when the ferrule is swaged minimum pressure will be exerted on the outer rubber and outer covering (the outer carcass). This particular improvement inhibits creep at the hose end (inboard) which is rounded as shown.
Turning now to the left end (nearest the connection—away from the hose) of the ferrule, there are a series of six ferrule grippers (having teeth, 12, and valleys, 13). The six teeth, in the prototype, actually vary in height from 5.75φ to 5.81φ while the ferrule valleys vary from 6.11φ to 6.17φ. (One embodiment considers the sine-wave lock concept used in the mid-section of the instant device.) The teeth will now be able to exert a varying force—on the reinforcement thereby eliminating potential ‘pinching’ of the reinforcement which will result in failure of the hose under pressure. The teeth are all approximately the same width and the valleys between the first five teeth (counting from the left) are the approximately the same width; however, the valley between the fifth and sixth tooth is somewhat wider. (In the embodiment employing the sine-wave lock, the valley width will vary.)
The stem of the corresponding prototype of the preferred invention is shown, in cross-section, in
It should be noted that no barbs are used in the instant invention (unlike the original Baldwin device shown in
As explained above, the relative position of the flutes on the stem and the nodes on the associated ferrule is critical to forming the sine-wave lock between the ferrule and the reinforcement which reduces the potential of creep when the inner tube is subjected to high temperature.
Moving towards the left in
It should be noted that in the region in which the flutes and grooves are employed the section of the stem forming the inside of the connector (where fluid flow is expected) is displaced. This is area 5 between region E and G. This is the area of the stem which will undergo internal expansion in order to start the sine-wave lock within area 5: It should be noted that no internal expansion occurs in the gripper area 3. An alternate embodiment that uses internal expansion in the gripper area may be employed and is not outside the scope of this disclosure.
Again, the dimensions given must not be construed as a restriction but as a sample. This is because dimensions will vary with the size of the fitting and the type of reinforced hose. Any engineer with knowledge of materials and swaging may readily make adjustments to this disclosure for varying sizes of fittings, hose, hose type and materials that could be used in the manufacturer of the fitting. In fact the size and position of the ridges, hollows, flutes and grooves should be chosen by trial and error to have a minimum height just so that the flutes and grooves cause the sine-wave lock of the reinforcement plys in the ferrule. The position of the flutes must be coordinated with the nodes of the ferrule so that after the two-step expansion and swaging operation, the sine-wave lock is obtained. A similar approach must be used when if the alternate sine-wave lock is used in the gripper section.
The ferrule of
The fitting is permanently attached to a reinforced high pressure rubber hose using industry standard techniques—yet another plus for the device. The outer covering is skived to expose the reinforcement. The axial skive length is set by the axial length of the ferrule: one must make certain that approximately ½-inch of the outer cover falls under the hose end of the ferrule before swaging. The inner tube is also skived to expose the reinforcement, but only to allow the grippers on the stem to come in contact with the reinforcement (this distance is set by the length of the gripper section on the stem). The hose is then carefully placed within the cavity formed between the ferrule and the stem to butt up against the stop point (B in
As explained earlier, the preferred connection between the hose and the end connector is a two-step process starting with internal expansion of the stem (
The second operation, namely the swaging operation, starts at the hose (inboard) end of the fitting and moves axially along the fitting to the termination (outboard) end. As the ferrule is swaged, it moves radially inward towards the stem and axially outward towards the hose. As the ferrule moves axially inward, the stem flutes act to displace all plys of the reinforcement into the nodes of the ferrule completing the sine-wave lock. At approximately midway along the ferrule (during swaging) the reinforcement at the hose end will lock in the form of a modified sine wave (following the shape of the ferrule). As the swaging operation continues, the ferrule will move axially away from the hose end of the fitting along with the hose. The sine wave lock progressively moves with the swage until swaging is stopped just past the point B (see
It must be understood that there is no mechanical lock between the inner tube of the hose and the stem. The mechanical lock occurs in the reinforcement gripper section of the connector. There is a secondary lock found between the nodes and flutes of the ferrule, in the form of a modified sine-wave, to the reinforcement. The inventive step is the realization that a series of sloped grippers interacting with the original Baldwin et al. sine-wave lock associated with an improvement to the termination area will serve to retain a high pressure-high temperature reinforced rubber hose inside a swaged end connector. The mechanical lock coupled with highly inventive inner tube dam and the modified sinusoidal wave lock in the body of the connector will inhibit elastomer creep within the reinforced hose (both the inner tube and the outer casing) during the swaging operation (COLD) under temperature (HOT). Thus, the series of cooperating inventive steps thereby ensure a leak-tight fitting at high temperature and pressure. The alternate gripper embodiment utilizing a sine-wave lock is a further inventive step. Thus the instant device is an improvement to the double-lock Baldwin device, adds to the art, and solves a critical industry problem—namely rubber creep during swaging and particularly under high operating temperatures.
Dimensions, materials of construction, the number of nodes/lands/flutes/grooves, and the number of ridges can vary with the size and duty of the hose assembly; thus, the disclosure given above must not be read as a limitation but as an example.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US12/00339 | 8/1/2012 | WO | 00 | 1/27/2014 |
| Number | Date | Country | |
|---|---|---|---|
| 61514596 | Aug 2011 | US |
